Pressure response type pulsation damper noise attenuator and accumulator

ABSTRACT

A pulsation damper and noise attenuator assembly comprising a housing having an inlet port and an outlet port fluidly connecting the interior of the housing to the flow path of the fluid flow system. A base is mounted to the housing and comprises a vent fluidly connecting the interior of the housing to an external fluid source. A sealing member such as an expandable bellows or piston is seated within the housing and creates a fluid tight seal between the fluid flow path and the external fluid source sealing member. The external fluid biases the sealing member in a forward direction. The sealing member acting against the N 2  fluid under pressure absorbs the full force of the hydraulic shock waves or pulsation within a high pressure fluid flow system as the assembly is mounted directly within the flow path of the fluid. The shock wave is exposed across the full face of the sealing member and dampened prior to the fluid continuing along the flow path.

This application is a continuation of patent application Ser. No.08/015,318, filed on Feb. 9, 1993 now abandoned, which is a division ofpatent application Ser. No. 07/749,127, filed on Aug. 23, 1991, now U.S.Pat. No. 5,205,326.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to a pulsation damper and noise attenuatorassembly for use in a fluid flow system. More particularly, the presentinvention relates to a pulsation damper and noise attenuator assemblythat is mounted directly in the fluid flow path of the fluid flowsystem.

II. Description of the Prior Art

A pulsation damper and noise attenuator assembly is generally used in afluid flow system to dampen or prevent development of pressure pulsationin a system where it is desired to continuously deliver fluids underpressure. Fluid pressure pumps, and, in particular positive displacementpumps create pressure pulsations during normal operation which can causeexcessive strain and/or damage to the conduits and within the fluidsystem. Further, the airborne sound generated by the pulsation travelingthrough the conduit may be very loud and poses an annoyance or possiblehazard to the user of the equipment.

To overcome these phenomenons, several prior art fluid devices have beendeveloped. A disadvantage of these previously known control device isthat the apparatus is not placed directly in the flow path of fluid butis instead usually coupled to the end of a T shaped connection. Removingthe prior art device from the fluid flow path prevents the device fromabsorbing the full force of the pulsation as the wave is not forced toflow directly through the device. Therefore, any pulsation thatinterrupts the fluid flow may not be suppressed by the device due to itsindirect application in the flow path.

A still further disadvantage of the prior art devices is that the fluidflow is not exposed to the complete surface area of the dampeningdevice. That is, the path of the pulsation is not directed across thefull face of the piston used to absorb the pulsation. Therefore,complete absorption or dampening of the pulsation is not provided by theprior art devices and, as such, the pulsation is allowed to dissipatethroughout the entire fluid flow path.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a pulsation damper and noise attenuatorassembly which overcomes the disadvantages of the previously known fluidcontrol apparatuses.

The pulsation damper and noise attenuator assembly of the presentinvention comprises a housing having an inlet port fluidly connecting afirst interior chamber of the housing to an external fluid pressuresource such as pressurized nitrogen. The housing, further comprises aninlet port and an outlet port which fluidly connect a second interiorchamber of the housing to the flow path of a fluid flow system such as,respectively, a fluid pump and a motor connect in an open and/or closedloop system.

A sealing member, such as an expandable bellows in a first embodiment ora free floating piston in a second embodiment, or other sealing memberssuch as a diaphragm, is seated within the interior of the housing (ofsuitable shape, e.g. cylindrical, round, spherical, etc.) and separatesthe housing interior into the first and second chambers.

In use the assembly inlet is in communication with a source of fluidunder pressure and all flow in the system passes through the secondaforementioned chamber. Therefore, any hydraulic shock wave or pulsationis directed into the assembly to allow the sealing member to absorb thepulsation. The sealing member counterbalances the high pressure fluid bythe external fluid, preferably an inert gas such as nitrogen, which iscommunicated under pressure to the first pressurized housing chamber.

Unlike the previously known fluid control apparatuses, the presentinvention provides that the force of a hydraulic shock waves orpulsations within the fluid flow system is directed across the entireforward face of the sealing member. By exposing the pulsations to alarger area, this insures that the pulsations will be absorbed by theassembly and dissipates the same with minimal affect on the highpressure fluid flow within the system. Further, by placing the assemblydirectly in the flow path of the fluid flow system the shock waves orpulsations is forced to be directed within the assembly and absorbedthereby.

Other advantages and features of the present invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood by reference to thefollowing detailed description of the preferred embodiments of thepresent invention when read in conjunction with the accompanyingdrawings, in which like reference characters refer to like partsthroughout the views, and in which:

FIG. 1 is a cross-sectional side view illustrating a first preferredembodiment of the present invention with the sealing member in its fullycontracted position;

FIG. 2 is a side cross-sectional view of the preferred embodiment ofFIG. 1 illustrating the sealing member in its fully expanded position;and

FIG. 3 is a side cross-sectional view illustrating a second preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 wherein there is illustrated a first preferredembodiment of the present invention in the form of a pulsation damperand noise attenuator assembly 10 which comprises a housing 12 formed ofan elongate hollow cylinder and sealed at one end by a valve assembly14. A base assembly 16 is mounted to the opposite end of the housing 12by suitable mounting means such as screws (or welded) 18. A seal such asan elastomer seal or metallic ring 20 about the perimeter of the baseassembly 16 creates a fluid tight seal between the housing 12 and thebase assembly 16. Valve assembly 14 is preferably mounted to the housing12 by welding (or screw-in) as shown at 22 and completely seals theinterior of the housing 12.

The valve assembly 14 includes a passageway 24 for fluidly connecting aninner chamber 42 of a sealing member to an external pressure fluidsource such as an inert gas, preferably nitrogen. In this preferredembodiment, the sealing member is preferably a bellows 30 that isexpandable and retractable in reaction to fluid pressure acting thereon.The bellows 30 is sealed at one end 32 to a member 36 having pressureresponse surface 34 and is movable therewith to expand and contract. Theopposite end 40 of the bellows 30 is mounted to support 28 of the valveassembly 14 to create a fluid tight assembly between the valve assembly14 and the bellows 30 to define the fluid tight inner chamber 42. Thefluid tight seal of the bellows 30 about the support 28 prevents thenitrogen from seeping into the interior chamber 26 of the housing 12.

Stops such as cylinders 44, 46 are mounted by bolts 48 to the support 28within the interior chamber 42 of the bellows 30. Cylinders 44, 46prevent the bellows 30 from retracting within the interior 26 of thehousing 12 beyond the faces 50 of the cylinders 44, 46. A check valve 54is provided within the passageway 24 to permit the entry of N₂ into thechamber 42 and prevent backflow of nitrogen from the chamber 42.

Base assembly 16 comprises an inlet port 56 and an outlet port 58fluidly connecting the interior chamber 26 of the housing 12 with theflow path of the fluid flow system. Preferably the inlet port isconnected in close proximity to the outlet of the source of the pressurepulsation, such as a piston pump. Mounting members such as ring 60 isfixedly mounted to the base assembly 16 by bolts 64 (or other permanentmounts such as welds or stops) within the interior 26 of the housing 12to limit the bellows 30 movement toward the inlet and outlet ports (seeFIG. 2).

Flow path A exemplifies the flow path of the fluid flowing within thesystem.

In use, the pulsation damper and noise attenuator assembly 10 isadvantageously placed directly within the flow path of the fluid flowassembly such as between a fluid pump and fluid motor. In this way, anyhydraulic shock waves or pulsations that develop in the high pressuresystem are directed into the assembly 10 to be dissipated by theretracting bellows 30. Further, the pulsation is exposed to the fullpressure responsive surface 34 of member 36 to be absorbed by thebellows 30 acting against the N₂ filled chamber under pressure toprovide a gas spring pulsation absorber. A larger area of deflection isafforded by this system.

Nitrogen from an external fluid source fills the inner chamber 42 of thebellows 30 to a predetermined pressure (e.g. 2000 psi) In its steadystate, bellows 30 is expanded to an intermediate position between thering 60 and the cylinders 44 and 46.

Pulsation within the fluid flow path flow along flow path A throughinlet port 56 of the assembly 10. The pulsation is absorbed by thebellows 30 acting against the N₂ chamber 42 and forces it to contract.The balancing force of the nitrogen within the bellows counters andreduces and/or eliminates pulsation. The pulsations are absorbed by thenitrogen spring within the bellows 36. The charge of N₂ is prepressuredto be between 50% and 70% of the pressure of the fluid system.

With reference now to FIG. 3, a second preferred pulsation damper andnoise attenuator assembly 110 is illustrated. In this embodiment, ahousing 112 comprises an inlet port 124 fluidly connecting an interiorchamber 142 of the housing 112 to an external-fluid source, preferablyan inert gas such as nitrogen so as to pressurize the chamber 142 to apredetermined amount, say 1500 psi.

A base assembly 116 is mounted to the housing 112 preferably by weldingmeans as shown at 122 (threaded or bolts or snap rings or other suitableretention means may be used) to create a fluid type seal between thehousing 112 and the base assembly 116.

Base assembly 116 comprises an inlet port 156 and an outlet port 158fluidly connecting the interior of the housing 112 to the flow path of afluid flow system.

A sealing member in the form of a free floating piston 130 is freelyslidable within the interior of the housing 112 and defines a movablewall of the inner chamber 142 that is exposed to the pressurizednitrogen and an outer chamber 144 exposed to the fluid within the flowpath of the assembly 110. Piston 130 comprises a seal such as anelastomer seal or a metallic ring 146 creating a fluid tight seal thatprevents the nitrogen from mixing with the fluid in the chamber 144.Piston 130 also comprises restraining means in the form of a ring shapedshoulder 148 extending around the perimeter of the piston 130.Restraining means 148 prevents the front face 136 of the piston 130 fromseating directly on the inlet and outlet ports 156 and 158.

In use, the assembly 110 is advantageously placed directly within theflow path of the fluid thereby directing the full force of the pulsationinto the assembly 110. Flow path A' is the direction of the fluid withinthe flow path of the system such as from a piston pump to a fluid motor.Flow path B' shows the flow path of the nitrogen as it is initiallydirected into the interior of the housing 112 to pressurize the chamber142. In use, inner chamber 142 is filled with nitrogen via the externalfluid source through the inlet port 124. The free floating piston 130 isstabilized within the system and seated as shown in FIG. 3. Fluid flowsthrough the inlet port 156 and is exposed to the entire outer face 136of the piston 130. The nitrogen counterbalances the force of the highpressure fluid against the entire face of the piston 136, forcing thepiston 136 to stabilize at some intermediate position while fluid flowsthrough to the outlet port 158 into the fluid flow path. When apulsation is developed within the system, the pulsation is directedacross the full outer face 136 of the piston 130. The excessive pressureforces the piston 130 rearward toward the inlet port 124 and, in turn,is forced into a forward position by the nitrogen counteracting thepulsation along the inner face 134 of the piston 130. Because the piston130 free floats within the interior of the housing 112 the excessiveforce created by the pulsation is dampened by the action of the pistonacting against the N₂ chamber 142 within the housing 112.

The spring rate may be further controlled by the use of a spring usedinside the chamber 42 and/or 142 as shown by the numeral 200 in FIGS. 2and 3.

Having described our invention, however, many modifications thereto willbecome apparent to those skilled in the art to which it pertains withoutdeviation from the spirit of the invention as defined by the scope ofthe appended claims.

What is claimed is:
 1. A pulsation damper and noise attenuator assemblyfor use in a liquid flow path of a fluid flow system comprising:anelongated housing having a cross sectional area and a longitudinal axiswith first and second ends; a base mounted to said housing at one enddefining an internal chamber in cooperation with said housing; a rigidmovable member having a pressure response surface extendingsubstantially parallel to the cross sectional area of said housing, saidmovable member disposed within said internal chamber of said housing forlongitudinal reciprocation, said movable member separating said internalchamber of said housing into an expandable first chamber and anexpandable second chamber; a fluid tight sealing member between saidmovable member and said housing for preventing fluid communicationbetween said first and second chambers; said first chamber of saidhousing having a gas pressurized to a predetermined level, such thatsaid movable member is normally disposed, during a stable steady liquidflow, in an intermediate position between said first and second ends ofsaid housing; an inlet port and an outlet port formed in said base, saidinlet port and said outlet port fluidly communicating with said secondchamber of said housing and adapted to connect said second chamber tothe liquid flow path of said fluid flow system, such that said liquidflow directly impacts the pressure response surface of said movablemember; stop means connected to one of the movable member and the basefor restraining forward movement of said movable member toward saidports, such that said first chamber is prevented from fully expandingwithin said housing and said ports are always in fluid communicationwith said second chamber; and said assembly is mounted directly in theliquid flow path of said fluid flow system and said liquid flow path isdirected normal to the pressure response surface of said movable member.2. The pulsation damper and noise attenuator assembly of claim 1 whereinsaid sealing member is a bellows.
 3. The pulsation damper and noiseattenuator assembly of claim 1 wherein said movable member is a piston.4. The pulsation damper and noise attenuator assembly of claim 3 whereinsaid sealing member is an annular seal ring disposed on said piston. 5.The pulsation damper and noise attenuator assembly of claim 1 furthercomprising a spring for biasing said movable member toward said base. 6.The pulsation damper and noise attenuator assembly of claim 5 whereinsaid spring is disposed in the first chamber.
 7. The pulsation damperand noise attenuator assembly defined in claim 1 further comprising asupport and stop means connected to the support for restraining rearwardmovement of said movable member such that said first chamber isprevented from fully contracting with said housing.